Embodiments of the present disclosure relate generally to improved debonding equipment and methods, and more particularly to debonding temporarily bonded wafers.
Several semiconductor wafer processes include wafer thinning steps. In some applications the wafers are thinned for the fabrication of integrated circuit (IC) devices. Thin wafers have the advantages of improved heat removal and better electrical operation of the fabricated IC devices. Wafer thinning also contributes to a reduction of the device capacitance and to an increase of its impedance, both of which result in an overall size reduction of the fabricated device. In other applications, wafer thinning is used for 3D-integration bonding and for fabricating through wafer vias.
Wafer thinning is usually performed via back-grinding and/or chemical mechanical polishing (CMP) of a wafer. CMP involves bringing the wafer surface into contact with a hard and flat rotating horizontal platen in the presence of liquid slurry. The slurry usually contains abrasive powders, such as diamond or silicon carbide, along with chemical etchants such as ammonia, fluoride, or combinations thereof. Polishing the wafer with the platen using the abrasive slurry thins the wafer, while the etchants polish the surface at the submicron level. The wafer is polished until a certain amount of substrate has been removed to achieve a targeted thickness.
For wafer thicknesses greater than 200 μm, the wafer is usually held in place with a fixture that utilizes a vacuum chuck or some other means of mechanical attachment. However, for wafer thicknesses of less than 200 μm and especially for wafer thicknesses of less than 100 μm, it becomes increasingly difficult to mechanically hold the wafer and also maintain control of the planarity and integrity of the wafer during thinning. In these cases, it is not uncommon for wafers to develop microfractures and break during CMP.
An alternative to directly holding a wafer during thinning involves attaching the device wafer (i.e., the processed wafer) to a carrier wafer for support and then thinning down the exposed opposite surface of the device wafer. The bond between the carrier wafer and the device wafer is temporary and the wafers are separated upon completion of the thinning (or other processing steps).